Catalyst systems for the polymerization of C2 -C10 -alk-1-enes

ABSTRACT

Catalyst systems for the polymerization of C 2  -C 10  -alk-1-enes contain, as active components, 
     a) a metallocene complex of the general formula I ##STR1## where M is a metal of subgroup III, IV or V of the Periodic Table of Elements or a metal of the lanthanide group, 
     X is halogen, hydrogen, C 1  -C 10  -alkyl, C 3  -C 10  -cycloalkyl, C 6  -C 15  -aryl, alkylaryl of 7 to 15 carbon atoms or --OR 15 , 
     R 15  is C 1  -C 10  -alkyl, C 6  -C 15  -aryl, alkylaryl, arylalkyl, fluoroalkyl or fluoroaryl, each having 1 to 10 carbon atoms in the alkyl radical and 6 to 20 carbon atoms in the aryl radical, 
     n is the valency of M minus two, 
     R 1  to R 14  are each hydrogen or C 1  -C 10  -alkyl or are each C 3  -C 10  -cycloalkyl which in turn may carry C 1  -C 10  -alkyl as substituent, or are each C 6  -C 15  -aryl or arylalkyl, where two adjacent radicals together may furthermore form a cyclic group of 4 to 15 carbon atoms, or are each Si(R 16 ) 3 , 
     R 16  is C 1  -C 10  -alkyl, C 6  -C 15  -aryl or C 3  -C 10  -cycloalkyl; 
     y 1 , y 2  are each CH 2 , C(R 17 ) 2 , Si(R 17 ) 2 , Ge(R 17 ) 2  or Sn(R 17 ) 2 , 
     R 17  is C 1  -C 10  -alkyl, C 6  -C 15  -aryl, C 3  -C 10  -cycloalkyl, alkylaryl or Si(R 18 ) 3  and 
     R 18  is C 1  -C 10  -alkyl, C 6  -C 15  -aryl, C 3  -C 10  -cycloalkyl or alkylaryl, 
     and 
     b) an open-chain or cyclic alumoxane compound of the general formula II or III ##STR2## where R 19  is C 1  -C 4  -alkyl and m is an integer from 5 to 30.

The present invention relates to catalyst systems for the polymerization of C₂ -C₁₀ -alk-1-enes, containing, as active components,

a) a metallocene complex of the general formula I ##STR3## where M is a metal of subgroup III, IV or V of the Periodic Table of Elements or a metal of the lanthanide group,

X is halogen, hydrogen, C₁ -C₁₀ -alkyl, C₃ -C₁₀ -cycloalkyl, C₆ -C₁₅ -aryl, alkylaryl of 7 to 15 carbon atoms or --OR¹⁵,

R¹⁵ is C₁ -C₁₀ -alkyl, C₆ -C₁₅ -aryl, alkylaryl, arylalkyl, fluoroalkyl or fluoroaryl, each having 1 to 10 carbon atoms in the alkyl radical and 6 to 20 carbon atoms in the aryl radical,

n is the valency of M minus two,

R¹ to R¹⁴ are each hydrogen or C₁ -C₁₀ -alkyl or are each C₃ -C₁₀ -cycloalkyl which in turn may carry C₁ -C₁₀ -alkyl as substituent, or are each C₆ -C₁₅ -aryl or arylalkyl, where two adjacent radicals together may furthermore form a cyclic group of 4 to 15 carbon atoms, or are each Si(R¹⁶)₃,

R¹⁶ is C₁ -C₁₀ -alkyl, C₆ -C₁₅ -aryl or C₃ -C₁₀ -cycloalkyl,

y¹, y² are each CH₂, C(R¹⁷)₂, Si(R¹⁷)₂, Ge(R¹⁷)₂ or Sn(R¹⁷)₂,

R¹⁷ is C₁ -C₁₀ -alkyl, C₆ -C₁₅ -aryl, C₃ -C₁₀ -cycloalkyl, alkylaryl or Si(R¹⁸)₃ and

R¹⁸ is C₁ -C₁₀ -alkyl, C₆ -C₁₅ -aryl, C₃ -C₁₀ -cycloalkyl or alkylaryl,

and

b) an open-chain or cyclic alumoxane compound of the general formula II or III ##STR4## where R¹⁹ is C₁ -C₄ -alkyl and m is an integer from 5 to 30.

The invention furthermore relates to the use of such catalyst systems for the preparation of polyalk-1-enes, processes for the preparation of polyalk-1-enes with the aid of these catalyst systems and the polyalk-1-enes obtainable thereby.

The patent literature, for example EP-A 69 951, describes many examples of unbridged, achiral metallocene complexes in conjunction with alumoxanes as catalysts for the polymerization of olefins. Stereoselective polymerizations are not possible with these systems. Furthermore, the introduction of chiral substituents in the cyclopentadienyl ring does not induce stereoselectivity in the polymerization of alk-1-enes with alumoxane as cocatalyst.

Makromol. Chem., Macromol. Symp. 48/49 (1991), 253-295 discloses that metallocene complexes which have a bridge between the cyclopentadienyl rings are suitable for stereospecific polymerizations of alk-1-enes. However, the synthesis of such compounds is expensive.

It is an object of the present invention to provide novel catalyst systems which are suitable for the uniform homopolymerization and in particular copolymerization of alkenes, give polymers having narrow molecular weight and comonomer distributions and are capable of stereoselectively polymerizing prochiral olefins.

We have found that this object is achieved by the catalyst systems defined at the outset and intended for the preparation of polyalk-1-enes. We have also found the use of such catalyst systems for the preparation of polyalk-1-enes, processes for the preparation of polyalk-1-enes with the aid of these catalyst systems and the polyalk-1-enes obtainable thereby.

The active components contained in the novel catalyst systems include one or more complexes of the general formula I: ##STR5##

M is a metal of subgroup III, IV or V of the Periodic Table of Elements or a metal of the lanthanide group, preferably a metal of subgroup IV or V, in particular titanium, zirconium or hafnium.

X is halogen, preferably chlorine, hydrogen, C₁ -C₁₀ -alkyl, preferably linear alkyl of 1 to 4 carbon atoms, in particular methyl or ethyl, C₃ -C₁₀ -cycloalkyl, preferably C₅ - or C₆ -cycloalkyl, C₆ -C₁₅ -aryl, preferably phenyl, alkylaryl of 7 to 15 carbon atom, preferably benzyl, or a group --OR¹⁵, where R¹⁵ is C₁ -C₁₀ -alkyl, C₆ -C₁₅ -aryl, alkylaryl, arylalkyl, fluoroalkyl or fluoroaryl, each having 1 to 10 carbon atoms in the alkyl radical and 6 to 20 carbon atoms in the aryl radical.

R¹ to R¹⁴, independently of one another, are each preferably hydrogen, C₁ -C₁₀ -alkyl, preferably C₁ -C₄ -alkyl, C₃ -C₁₀ -cycloalkyl, preferably C₅ - or C₆ -cycloalkyl, which in turn may carry C₁ -C₁₀ -alkyl as a substituent, C₆ -C₁₅ -aryl, preferably phenyl, or arylalkyl, preferably benzyl. It is also possible for two adjacent radicals, ie. R¹ and R², R² and R³, R⁵ and R⁶ or R⁶ and R⁷ and R⁸ and R⁹, R⁹ and R¹⁰, R¹² and R¹³ or R¹³ and R¹⁴, together to form a cyclic group of 4 to 15 carbon atoms, which may furthermore be aromatic; two adjacent radicals preferably form a 6-membered ring.

R¹ to R¹⁴ may furthermore be Si(R¹⁶)₃, where R¹⁶ is C₁ -C₁₀ -alkyl, C₆ -C₁₅ -aryl or C₃ -C₁₀ -cycloalkyl.

Particularly suitable compounds of the general formula I are those in which R¹ to R¹⁴ are chosen so that symmetrical compounds are formed, ie., for example, R¹ and R⁸ are identical, as are R² and R⁹, R³ and R¹⁰, R⁴ and R¹¹, R⁵ and R¹², R⁶ and R¹³ and R⁷ and R¹⁴. Particularly preferred compounds of the general formula I are those in which all radicals R¹ to R¹⁴ are hydrogen.

y¹ and y² may be identical or different and are each CH₂, C(R¹⁷)₂, Si(R¹⁷)₂, Ge(R¹⁷)₂ or Sn(R¹⁷)₂, Si(R¹⁷)₂ being preferred. R¹⁷ is C₁ -C₁₀ -alkyl, preferably C₁ -C₄ -alkyl, in particular methyl, C₆ -C₁₅ -aryl, preferably phenyl, C₃ -C₁₀ -cycloalkyl, preferably C₅ -C₆ -cycloalkyl, alkylaryl, preferably benzyl, or Si(R¹⁸)₃, where R¹⁸ is C₁ -C₁₀ -alkyl, C₆ -C₁₅ -aryl or C₃ -C₁₀ -cycloalkyl or alkylaryl.

Such complexes can be synthesized by conventional methods, the reaction of the corresponding ligands with, for example, butyl-lithium and subsequent addition of MX_(n+2) being preferred.

Examples of corresponding preparation processes are described in, inter alia, J. Organometal. Chem. 369 (1989), 359-370.

The metallocene complexes may also be present in cationic form, as described in EP-A 277 003 and EP-A 277 004.

In addition to the metallocene complexes, the novel catalyst systems also contain oligomeric alumoxane compounds.

For example, open-chain or cyclic alumoxane compounds of the general formula II or III ##STR6## where R¹⁹ is C₁ -C₄ -alkyl, preferably methyl or ethyl, and m is an integer from 5 to 30, preferably from 10 to 25,

are suitable.

The preparation of these oligomeric alumoxane compounds is usually carried out by reacting a solution of a trialkylaluminum with water and is described in, inter alia, EP-A 284 708 and U.S. Pat. No. 4,794,096.

As a rule, the oligomeric alumoxane compounds obtained are in the form of mixtures of both linear and cyclic chain molecules of different lengths, so that m is to be regarded as an average value. The alumoxane compounds may also be present as a mixture with other metal alkyls, preferably with alkylaluminums.

It has proven advantageous if the atomic ratio of aluminum from the oligomeric alumoxane compound to the metal M from the metallocene complex is from 10:1 to 10⁶ :1, preferably from 10:1 to 10⁴ :1.

The components of the novel catalyst systems may be introduced into the polymerization reactor individually in any sequence or as a mixture.

With the aid of these catalyst systems, it is possible to prepare polymers of alk-1-enes. These are understood as being homo- and copolymers of C₂ -C₁₀ -alk-1-enes, preferably used monomers being ethylene, propylene, but-1-ene, pent-1-ene and hex-1-ene.

The preparation of these polymers may be carried out either batchwise or, preferably, continuously in the conventional reactors used for the polymerization of alkenes. Suitable reactors include continuously operated stirred kettles, and it is also possible to use a plurality of stirred kettles connected in series.

In a preferred embodiment, the oligomeric alumoxane compound, preferably in the form of a solution in an inert solvent, for example in benzene, toluene, hexane, heptane or a mixture thereof, is initially taken and is heated to 20°-80° C. The metallocene complex, which is preferably in solution in an inert solvent, in particular in the solvent in which the oligomeric alumoxane compound is also dissolved, is then added.

The polymerization conditions are in principle not critical; pressures of from 0.5 to 3000, preferably from 1 to 80, bar and temperatures of from -50° to +300° C., preferably from -20° to 100° C., have proven suitable.

Polymerization reactions with the aid of the novel catalyst systems can be carried out in the gas phase, in suspension, in liquid monomers or in inert solvents. In the polymerization in solvents, in particular liquid hydrocarbons, such as benzene or toluene, are used. Polymers having good performance characteristics are also obtainable in the polymerization in the gas phase, in suspension and in liquid monomers.

The average molecular weight of the polymers formed can be controlled by the methods usually used in polymerization technology, for example by adding regulators such as hydrogen, or by changing the reaction temperatures.

The novel catalyst systems have very high productivity.

EXAMPLES Example 1

Preparation of a titanium complex of the formula Ia ##STR7## 5.79 g (=23.7 mmol) of ##STR8## were dissolved in 150 ml of toluene, and 15.0 ml of a 1.58 molar solution of n-butyllithium in hexane (=23.7 mmol) were added at room temperature. For complete conversion, stirring was carried out for 12 hours. Thereafter, the white suspension prepared was slowly added dropwise at -100° C. to a solution of 2.25 g (=11.9 mmol) of TiCl₄ in 150 ml of toluene, and the mixture was allowed to warm up to room temperature. The bright red solution obtained was filtered off from the undissolved matter, the residue was washed with hexane (2×20 ml) and the solvent was completely removed under greatly reduced pressure. The residue was taken up with 100 ml of hexane and crystallized at -30° C. The bright red needles were isolated and were dried under greatly reduced pressure.

Yield: 3.30 g (=46%)

Melting point: 152° C.

The substance was stable in air and readily soluble in organic solvents.

Analytical data for the compound Ia:

¹ H-NMR (CDCl₃): δ=-0.69, 0.38, 0.40, 0.53 (4s, 4x6H, 4xCH₃), 4.85 (br. s, 2H, 2xallyl. H), 6.31 (br. s, 2H, H-5, H-5'), 6.76 (m, 2H, H-11, H-11'), 6.91 (m, 2H, H-12, H-12'), 6.97 (br. s, 4H, H-4, H-6, H-4', H-6'), 7.07 (br. s, 2H, H-10, H-10').

¹³ C{¹ H}-NMR (CDCl₃): δ=-5.58, -1.02, 1.26 (br.; 4xCH₃), 55.94 (allyl. C), 114.86 (vinyl. CH), 131.68 (C-5,C-5'), 133.82 (C-4, C-6, C-4', C-6'), 139.45, 140.09 (vinyl. CH), 142.04 (br., C-3, C-7, C-3', C-7') 144.10 (vinyl. C).

²⁹ Si-NMR (CDCl₃): δ=-1.73, -17.47.

MS: m/z (rel. Int. [%])=605 (M⁺, 45), 570 ((M-³⁵ Cl),26), 361 ((M-(1),100), 326 ((M-(1)-³⁵ Cl),62), 290 ((M-(1)-2x³⁵ Cl),50), 274 ((M-(1)-2x³⁵ Cl-CH₃),12), 244 ((M-(1)-2x³⁵ Cl-⁴⁸ Ti),22).

C₂₈ H₃₈ Cl₂ Si₄ Ti (605.1) Calculated C 55.52 H 6.28 Found C 54.26 H 6.54

Examples 2 to 5

Preparation of polyethylene (PE) with Ia

450 ml of toluene were initially taken in a 1 l steel autoclave and heated to various temperatures, and 6.15 ml (=10.26 mmol) of a 1.6 molar solution of methyl alumoxane (MAO) in toluene were added. 6.16 mg (=0.0102 mmol of Ti) of Ia in the form of a solution in toluene (1 mg/ml) were then added. The atomic ratio of Al from MAO to Ti from Ia was 1000:1. The autoclave was then purged with ethylene under various pressures. After a polymerization time of 60 minutes, the pressure was let down and the PE formed was freed from adhering solvent by expelling the toluene with steam and was dried.xs.

The experimental conditions and the properties of the polyethylenes formed are listed in the table.

The Staudinger index [η] was determined at 135° C. in decalin.

                  TABLE                                                            ______________________________________                                                       Yield                                                                   Tempera- pres-           [g of                                                 ture     sure            PE/g of [η]                                Example                                                                               [°C.]                                                                            [bar]   [g of PE]                                                                              Ia]     [cm.sup.3 /g]                          ______________________________________                                         2      30       9       1.8     290     520                                    3      50       9       5.9     960     740                                    4      80       9       0.7     113     230                                    5      50       18      7.5     1220    1110                                   ______________________________________                                     

We claim:
 1. A catalyst system for the polymerization of C₂ -C₁₀ -alk-1-enes, containing, as active components,a) a metallocene complex of the formula I ##STR9## where M is a metal of subgroup III, IV or V of the Periodic Table of Elements or a metal of the lanthanide group,X is halogen, hydrogen, C₁ -C₁₀ -alkyl, C₃ -C₁₀ -cycloalkyl, C₆ -C₁₅ -aryl, alkylaryl of 7 to 15 carbon atoms or --OR¹⁵, R¹⁵ is C₁ -C₁₀ -alkyl, C₆ -C₁₅ -aryl, alkylaryl, arylalkyl, fluoroalkyl or fluoroaryl, each having 1 to 10 carbon atoms in the alkyl radical and 6 to 20 carbon atoms in the aryl radical, n is the valency of M minus two, R¹ to R¹⁴ are each hydrogen or C₁ -C₁₀ -alkyl or are each C₃ -C₁₀ -cycloalkyl optionally substitued by C₁ -C₁₀ -alkyl, or are each C₆ -C₁₅ -aryl or arylalkyl, where two adjacent radicals together may furthermore form a cyclic group of 4 to 15 carbon atoms, or are each Si(R¹⁶)₃, R¹⁶ is C₁ -C₁₀ -alkyl, C₆ -C₁₅ -aryl or C₃ -C₁₀ -cycloalkyl, y¹, y² are each CH₂, C(R¹⁷)₂, Si(R¹⁷)₂, Ge(R¹⁷)₂ or Sn(R¹⁷)₂, R¹⁷ is C₁ -C₁₀ -alkyl, C₆ -C₁₅ -aryl, C₃ -C₁₀ -cycloalkyl, alkylaryl or Si(R¹⁸)₃ and R¹⁸ is C₁ -C₁₀ -alkyl, C₆ -C₁₅ -aryl, C₃ -C₁₀ -cycloalkyl or alkylaryl,and b) an open-chain or cyclic alumoxane compound of the formula II or III ##STR10## where R¹⁹ is C₁ -C₄ -alkyl and m is an integer from 5 to
 30. 2. The catalyst system of claim 1, wherein M is a metal of subgroup IV of the Periodic Table of Elements.
 3. The catalyst system of claim 1, wherein y¹ and y² are each Si(R¹⁷)₂.
 4. A polymer of C₂ -C₁₀ -alk-1-enes, obtained by a process as defined in claim
 1. 5. A process for the preparation of polymers of C₂ -C₁₀ -alk-1-enes which comprises polymerizing a C₂ -C₁₀ -alk-1-ene at from 0.5 to 3000 bar, and at from -50° to 300° C. in the presence of the catalyst system of claim
 1. 